Session: Session 4

Penetration Profiles of Four Topical Antifungals in Mycotic Human Toenails Quantified by Matrix‑Assisted Laser Desorption Ionization–Fourier Transform Ion Cyclotron Resonance Imaging

INTRODUCTION:

We present here the use of MALDI Mass Spectrometry Imaging (MALDI-MSI) for the quantitative analysis of antifungal distribution in nails to provide useful insights into whether drug exposure is sufficient to result in treatment success.

METHODOLOGY:

Antifungal compounds (amorolfine, ciclopirox, naftifine, and tioconazole) were applied to mycotic nails at a dose of 10 µL/cm2. The midline cross sections of the toenails were mounted onto adhesive tape, placed on slide and then MALDI matrix was sprayed over the toenail sections with an automatic sprayer system. The nail sections were then analyzed with a 7 T MALDI-FTICR.

Absolute quantification was obtained and based on published data on the minimum inhibitory concentrations (MIC) of the four test compounds needed to inhibit 50% and 90% (MIC50 and MIC90) of Trichophyton rubrum, the fold differences between the MIC and the anti‑fungal concentrations in the nails (termed the multiplicity of MIC) were calculated for each.

RESULTS:

The penetration profiles indicated higher concentrations of amorolfine and ciclopirox in the deeper layers of the nails 3 h after treatment, compared with naftifine and tioconazole. The mean concentrations across the entire nail sections at 3 h were significantly different among the four antifungals: amorolfine, 2.46 mM; ciclopirox, 0.95 mM; naftifine, 0.63 mM; and tioconazole, 1.36 mM (p=0.016; n = 8 per compound). The median multiplicity of the MIC90 at 3 h was 191-fold for amorolfine, 10-fold for ciclopirox, 52-fold for naftifine, and 208-fold for tioconazole.

CONCLUSION:

This is the first report describing the use of MALDI-FTICR for the quantitative analysis of antifungal distribution in nails. Ex vivo, amorolfine achieved a high MIC90 multiplicity and a higher fungicidal concentration in the nail than ciclopirox, naftifine, or tioconazole within 3 h of application, suggesting that this antifungal compound may offer greater antifungal efficacy.